Dissolved vanadium in rivers: effects of silicate weathering

New measurements of vanadium in 15 small California catchments as well as some tributaries of the Mississippi River are presented here, These measurements complement previously published fluvial vanadium data and allow a re-examination of prior conclusions about the geochemistry of vanadium in rivers. The data suggest a best estimate of the fluvial flux of dissolved vanadium to be 0.52 Gmol year(-1), though considerable uncertainty remains in this number. Dissolved vanadium in rivers appears to be derived largely from the weathering of silicate rocks which leads to a general correlation between dissolved V and Si in rivers. However, rock type can modify this basic correlation as can solubility limits on Si. The nature of the erosional regime may play some role in modifying fluvial V/Si ratios, but the effect is weak enough to be obscured by other factors. Fluvial vanadium transport is also potentially affected both by organic matter (through complexation and reduction) and by the effects of oxygen depletion in lakes, reservoirs and fresh water sediments. However, these factors require additional study. The development of methodology to determine vanadium redox speciation in the field would aid the further understanding of the processes affecting the transport of this element through the environment. (C) 2000 Elsevier Science B.V. All rights reserved.